HONG KONG, Dec. 31 -- Hong Kong authorities said on Wednesday that they will cull thousands of chickens to prevent an outbreak of bird flu.

Authorities will slaughter 15,000 chickens at the Cheung Sha Wan market following the latest discovery of the deadly H7N9 virus in poultry imported from south China's Guangdong province, said the city's Secretary for Food and Health Ko Wing-man.

A batch of chickens imported from Huizhou city in Guangdong province tested positive for the virus through a "rapid testing" program.

The market will then be closed for 21 days for thorough cleansing and disinfection, Ko said, adding that trading of live poultry will be suspended during the closure period.

He said the government has built up a resilient and stringent system and collaborated closely with the mainland authorities for the surveillance and control of avian influenza.

Meanwhile, Hong Kong announced it was raising its response level in hospitals to "serious" from "alert" with extra precautions implemented from Sunday in response to a new case of the avian influenza virus -- the region's first since early 2014.

On Dec. 25, a 68-year-old woman was hospitalized in Hong Kong after arriving from the neighboring mainland city of Shenzhen almost two weeks earlier.